1. Field of the Invention
The invention relates to polyol blends to be used in flexible polyurethane foams and more particularly relates to such blends and foams which use an aromatic polyester polyol made from recycled polyethylene terephthalate and alkylene glycol and dibasic acid waste streams.
2. Description of Relevant Compounds and Methods in the Field
Flexible polyurethane foams are widely used as cushioning materials in furniture and automotive seating, mattresses and the like. They are made generally like other types of foams; that is, a polyol is reacted with a polyisocyanate in the presence of a polyurethane-forming catalyst such as a tertiary amine or an organotin compound. Frequently, other materials are added such as silicone surfactants, fire retardants, blowing agents, etc. U.S. patents which are concerned with flexible polyurethane foams include U.S. Pat. Nos. 3,535,307; 3,847,992; 4,316,991; 4,338,408 and 4,342,687, among others.
The recovery of polyalkylene terephthalate scrap or residues has long been practiced. U.S. Pat. No 3,344,091 describes a process for converting scrap polyester, such as polyethylene terephthalate (PET) into active prepolymer particles by mixing the scrap PET with the glycol originally used in preparing PET, with or without the additional presence of a lower dialkyl ester of the aromatic dicarboxylic acid whose dehydroxylated residues are present in the scrap PET. Chemical Abstracts (CA), vol. 84, paragraph 5638h, relates that British Pat. No. 1,458,486 teaches dialkyl terephthalates, such as dimethyl terephthalate (DMT), recovery by heating scrap PET with monohydric alcohols with a catalyst and a sequestering agent.
PET scrap may be recovered by depolymerization with glycols as seen in CA 78:160452n, abstract to East German Pat. No. 92,801. U.S. Pat. No. 4,166,896 teaches that a mixture of glycols and oligomers (such as low molecular weight polyesters of terephthalic acid and a glycol) may be depolymerized (transesterified) by heating. Subsequently, ethylenically unsaturated dicarboxylic acids or their anhydrides are added and the mixture is heated again. An unsaturated polyester resin is produced. A suitable dicarboxylic acid is phthalic acid, the anhydride of which is also useful in this process.
Scrap polyalkylene terephthalate, such as polyethylene terephthalate is known to be incorporated into polyurethanes. For example, U.S. Pat. No. 4,048,104 relates that polyisocyanate prepolymers for use in polyurethane products may be prepared by combining an organic polyisocyanate with polyols which are the hydroxyl-terminated digestion products of waste polyalkylene terephthalate polymers and organic polyols. A polyol ingredient which is the digestion product of polyalkylene terephthalate residues or scraps digested with organic polyols is also described in U.S. Pat. No. 4,223,068. Another case where terephthalic acid residues are employed is outlined in U.S. Pat. No. 4,246,365 where polyurethanes are made from polyesters containing at least two hydroxyl groups and terephthalic acid residues.
More relevant to the compounds of this invention is the solution proposed in U.S. Pat. No. 4,237,238. In this patent, a polyol mixture is prepared by the transesterification of a residue from the manufacture of dimethyl terephthalate with a glycol, which is then used to produce polyisocyanurate foams having a combination of a higher degree of fire resistance with low smoke evolution, low foam friability and high compressive strength. The preparation of such a polyol mixture (from ethylene glycol and dimethyl terephthalate esterified oxidate residue) is described in U.S. Pat. No. 3,647,759. J. M. Hughes and John Clinton, in the Proceedings of the S.P.I. 25th Annual Urethane Division Technical Conference, Scottsdale, Ariz. (October 1979), describe other foams prepared from the polyols of U.S. Pat. No. 3,647,759.
U.S. Pat. No. 3,755,212 teaches air blown polyurethane foams prepared from ester-modified polyether polyols, a polyisocyanate and a polyurethane catalyst. The modifying agents for reaction with the polyols apparently are internal anhydrides of polycarboxylic acids, such as phthalic anhydride. Rigid polyurethane foams may be made from a fluid polyol made by hydrogenating a DMT process residue, then reacting the hydrogenation product with an alcoholic material, according to U.S. Pat. No. 3,892,796. Further, U.S. Pat. No. 4,186,257 reveals that high molecular weight polyurethanes from polyols linked with ester groups may be made by reacting diols with phthalic acid or DMT. Polybutylene terephthalate diols and polyhexamethylene terephthalate diols are also used.
Brominated ester-containing polyether polyols may be prepared by the sequential reaction of a polyether polyol with 4,5-dibromohexahydrophthalic anhydride and an alkylene oxide according to U.S. Pat. No. 4,069,207. Flame-retardant polyurethane foams are prepared using these modified polyols. Also relevant is East German Pat. No. 122,986 cited in CA 86:190834w which teaches that polyurethanes may be manufactured from polyester polyols made by condensation and transesterification of PET synthesis distillation residues with polyols, polyamino alcohols and fatty acid ester diols.